Reference signal generator for return path aligning

1. A cable television system, comprising: head-end equipment including: forward means for providing multiple streams of electrical data signals including television signals and telephone signals from a telephone system, combining the multiple streams into a smaller number of at least one forward stream of electrical data signals, converting the forward stream of electrical signals into a forward stream of optical signals and transmitting the forward optical stream; and return means for receiving at least one return stream of optical data signals including telephone signals and a reference signal, converting the return stream of optical signals into a return stream of electrical signals, amplifying the strength of the electrical return signals, routing the return telephone signals to a telephone system, and detecting the reference signal; a plurality of nodes including: system means for receiving the combined forward stream of optical signals, converting the forward optical signals into forward electrical signals, amplifying the forward electrical signals, and transmitting the forward electrical signals; and return means for receiving one of more return streams of electrical data signals from customers, amplifying the return electrical signals, generating a return reference signal, combining the return reference signal with the customer return signals, converting the electrical return signals into optical return signals; and means for transmitting the optical return signals; a forward optical fiber network for distributing the optical signals transmitted from the head-ends to the nodes; a return optical fiber network for collecting the return optical signals transmitted from the nodes into the head-end; and a plurality of customer interface units for receiving the forward electronic signals from the nodes and transmitting the return electrical signals to the nodes; and a coaxial cable network for distributing the forward electronic signals transmitted from the nodes to the customer interface units and for returning the customer return signals transmitted from the customer interface units to the nodes.

2. The system of claim 1 , in which: the head-end equipment includes control signal means for generating a reference control signal and means for combining the reference control signal into the forward signals for distributing the reference control signal to the nodes; and the nodes further include reference control means for controlling the generating of the return reference signal depending on the reference control signal.

3. The system of claim 2 , in which: the control signal means include activation control means for providing signals to control toggling the reference signal generation on and off, and the reference control means include means for toggling the reference signal generation on and off depending on the activation control signals.

4. The system of claim 3 , in which: the control signal means include frequency control means for providing signals to control the frequency of the transmitted reference signal, and the reference control means include means for controlling the frequency of the reference signal depending on the frequency control signals.

5. The system of claim 3 , in which: the control signal means include amplitude control means for providing signals to control the amplitude of the transmitted reference signal, and the reference control means include means for controlling the amplitude of the reference signal depending on the amplitude control signals.

6. The system of claim 3 , in which: the return means includes means for automatically monitoring the return reference signal for verifying the operation of the return distribution system.

7. The system of claim 3 , in which: the control signal means includes means for selectively addressing individual nodes of the distribution systems to control the generation of the reference control signals differently at different nodes.

8. The system of claim 7 , in which: the head-end equipment includes means for selecting one of the nodes; the control signal means includes means to signal the selected node to modifying the reference signal; and the return means includes means for detecting the modification of the reference signal so as to verify that the forward and return networks are both functioning correctly for that node.

9. The system of claim 1 , in which the forward and return electrical and optical signals include modulated radio-frequency analog signals; the forward means of the head-end include multiple optical transmitters and the nodes include multiple optical receivers; the nodes include multiple optical transmitters each with a respective oscillator for producing a respective reference signal and each with a respective controller for controlling the oscillator depending on respective reference control signals; the head-end forward means is adapted for each transmitter, to modulate each of the multiple streams of electrical signals at a different frequency and to combine the streams of different frequency to provide the combined electrical stream; at least one node includes multiple optical receivers and is connectable to multiple coaxial cable networks and includes a router for routing telephone data streams in the combined data stream to a selected one of the coaxial cable networks connected to the node; a node includes means to re-modulate a telephone stream to a selected frequency.

10. A cable television head-end, comprising: means for receiving multiple streams of electrical data signals; means for combining the multiple data streams into fewer streams including at least one forward stream of electrical signals; means for converting the electrical forward data stream into a forward optical signal and transmitting the forward optical signal; means for receiving an optical return signal including a reference signal; means for converting the optical return signal into a return stream of electrical signals; means for amplifying the strength of the electrical return signals; and means for detecting the presence of the reference signal in the return signal.

11. The head-end of claim 6 , further comprising: multiple receivers for receiving respective optical return signals including a reference signal and for converting the optical signals into electrical return signals; means for measuring the signal level of the reference signal for each receiver; means for adjusting the level of the return signals in order to align the level of the reference signals in the return system.

12. A node in a cable television distribution system, comprising: means for receiving at least one forward optical data stream; means for converting the optical forward signal stream into electrical signals; means for amplifying the forward electrical signals; means for transmitting the forward electrical signals; means for receiving electrical customer return signals; means for amplifying the electrical return signals; means for generating a return reference signal; means for combining the return reference signal with the customer return signals; means for converting the electrical return signals into optical return signals; and means for transmitting the optical return signals onto an optical return signal distribution system.

13. A return signal circuit, comprising: means for receiving control signals; means for receiving electrical customer data signals; means for amplifying the customer data signals; means for modulating the customer signals with a selected carrier frequency; means for generating an electrical reference signal depending on the control signals; means for combining the electrical customer signals with the electrical reference signal into a return signal; means for converting the electrical return signal into optical return signal.

14. A node for a cable television distribution system, comprising: an optical receiver circuit for receiving a forward optical signal and converting the optical signal into an forward electrical signal; a connection for receiving electrical return signals from customers; an optical transmitter circuit, including: a laser modulated by the electrical return signal for converting the electrical return signal into an optical return signal depending on laser control signals; an oscillator circuit for producing an electrical reference signal depending on reference control signals; means for combining the electrical reference signal into the electrical return signal before converting the return signal from an electrical signal into an optical return signal; and a monitor circuit for producing electrical status signals; a signal processor including: a circuit for extracting the control signals from the forward electrical signals; a circuit for transmitting respective control signals to the laser and the oscillator circuit; and a circuit for modulating the status signals at a selected frequency; means for combining the modulated electrical status signals into the electrical customer return signals to produce the electrical return signal.

15. The node of claim 14 , in which: the node further comprises optical connectors for attaching an optical cable to receive the forward optical signal and a plurality of electrical connectors for attaching coaxial cables for transmitting the forward electrical signals and for receiving electrical return signals from the customers; and a respective separator for filtering customer return signals from the forward electrical signal; a modulator for re-modulating the return signals from each attached coaxial cable at a different frequency; the extracting circuit is adapted to extract from the forward signal: control signals for toggling the return reference signal on and off, control signals for changing the frequency of the reference signal, and a control signals for changing the amplitude of the reference signal.

16. A head-end for communicating with distribution nodes, comprising: a computer system including: a user interface; at least one output port; at least one input port; a processing unit communicating with the terminal and ports; electronic memory communicating with the processing unit and programmed to provide apparatus, including: means for receiving and displaying status information for respective nodes, received through the input port; means to allow a human operator to select a node and to input commands for the node including commands to toggle the reference signal for the selected node between on and off; means to transmit command signals through the output ports; means to receive status information through the input ports; means to display the status information to the human operator; one or more transmitters communicating with respective computer output ports and including: means for receiving multiple electrical signals including the control signals; means for combining the different signals into an electrical forward distribution signal; and a laser for converting the electrical forward signal into an optical forward signal; a plurality of receivers communicating with one or more of the computer input ports and including: means for receiving an optical return signal; means for detecting the presence and measuring the amplitude of an optical reference signal embedded in the return signal for aligning the receivers; means for converting the optical return signal into an electrical return signal including status signals and including a signal indicating the presence of each respective reference signal of each node.

17. The head-end of claim 16 , in which: the transmitters are connected to one or more computer output ports through a respective modulator for each output port and/or for each transmitter; the receivers are connected to one or more computer input ports through a respective demodulator for each input port and/or for each receiver; the head-end further comprises means for providing signals indicating the frequency and amplitude of the reference signals; the status signals for each node, include signals indicating: the bias current of the laser, the optical output power of the laser, the amplitude of the reference signal, the frequency of the reference signal, and the operation of the transmitter of the node; the commands further include: commands to toggle the transmitter of the selected node between on and off, commands to select the amplitude of the reference signal, and commands to select the frequency of the reference signal.

18. A transmitter circuit for a node of a cable television system, comprising: one or more coaxial cable inputs for electrical customer return signals; an oscillator for generating an electrical reference signal; an input for reference control signals including a signal to toggle the reference oscillator between on and off and for laser control signals including a signal to turn the laser on and off; a coupler for combining the reference signal into the customer return signals to provide an electrical return signal; an amplifier for increasing the level of the electrical return signal; a laser for converting the amplified electrical return signal into an optical return signal; an optical cable output connection for the optical return signal.

19. The transmitter circuit of claim 18 , in which: the circuit further comprises a gain adjust for each customer signal input; the circuit further comprises a gain adjust for the reference signal; the circuit further comprises a gain adjust for the amplified return signal to provide the correct signal level to the laser; the circuit further comprises a slope adjust for the amplified return signal; the circuit further comprises one or more monitors for generating the status signals including status signals for optical power output and laser bias current and another coupler for combining the status signals into the return signal; and the input for reference control signals is adapted for receiving a signal to adjust the frequency of the reference oscillator and a signal to adjust the amplitude of the reference signal.